using System;

 using System.Collections.Generic;

 using System.Linq;

 using System.Web;

 using System.Web.UI;

 using System.Web.UI.WebControls;

 using System.Drawing;

 using System.Drawing.Drawing2D;

 using System.Drawing.Imaging;

 public partial class _Default : System.Web.UI.Page

 {

     protected void Page_Load(object sender, EventArgs e)

     {

         //生成随机生成器

         Random random = new Random();

         //成语字符串数组，随机去除创建验证码

         string[] str = { "海阔天高", "望子成龙", "守株待兔", "国足无敌", "点石成金", "天涯明月", "尧尧无敌", "一望无际" };

         //string checkCode = "海阔天高";

         int count = random.Next(str.Length);

         string checkCode = str[count];

         //根据字符串长度创建一个Bitmap画布

         Bitmap image = new Bitmap((int)Math.Ceiling((checkCode.Length * 20.5)), );

         Graphics g = Graphics.FromImage(image);

         try

         {

             g.Clear(Color.White);//清空图片背景色

             for (int i = ; i < ; i++)//生成两条随机的噪音线

             {

                 int x1 = random.Next(image.Width);

                 int x2 = random.Next(image.Width);

                 int y1 = random.Next(image.Height);

                 int y2 = random.Next(image.Height);

                 g.DrawLine(new Pen(Color.Black), x1, y1, x2, y2);

             }

             Font font = new Font("Arial", , (FontStyle.Bold));//定义字体

             LinearGradientBrush brush = new LinearGradientBrush(

                 new Rectangle(, , image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2f, true);

             g.DrawString(checkCode, font, brush, , );

             //画图片前景噪音点

             for (int i = ; i < ; i++)

             {

                 int x = random.Next(image.Width);

                 int y = random.Next(image.Height);

                 image.SetPixel(x, y, Color.FromArgb(random.Next()));

             }

             //画图片边框线

             g.DrawRectangle(new Pen(Color.Silver), , , image.Width - , image.Height - );

             System.IO.MemoryStream ms = new System.IO.MemoryStream();

             image.Save(ms, ImageFormat.Gif);

             Response.ClearContent();

             Response.ContentType = "image/Gif";

             Response.BinaryWrite(ms.ToArray());

         }

         finally

         {

             g.Dispose();

             image.Dispose();

         }

     }

 }